This invention relates to a multi-color printing apparatus to produce multi-color printing by the stencil printing technique while the printing paper makes one pass through the apparatus. It uses image transferring sections provided for the respective colors to transfer color images onto the printing paper and selectively moves the stencil supplying/discharging means which includes an original printing stencil supplying device and a used printing stencil collecting device.
A conventional, multi-color printing apparatus for printing multiple color images onto a single sheet of paper is constructed with printing sections of the stencil rotary press arranged in a tandem configuration. In this type of multi-color printing apparatus, the original printing stencils having the different images for the respective colors are created by the original printing stencil creating device which is arranged separately from the printing apparatus and the respective original printing stencils are manually mounted on the printing drums of the respective printing sections.
If images printed in different printing cycles are deviated from one another, the image will be printed as multiple or overlapping images. In order to prevent deviation in the printing position, the feeding operations of the printing paper feeding mechanisms are synchronized with one another.
Further, the above printing deviation is caused not only by the printing paper feeding mechanism but it can also be caused when the original printing stencils are created or they are mounted on the printing section. Therefore, after the original printing stencils are mounted on the printing drum, a trial printing is conducted to check whether there is a printing deviation or not. If there is a printing deviation, the mounting position of the original printing stencil is corrected to eliminate it.
The printing stencil (called a used printing stencil) is left on the screen after the printing operation is completed to prevent ink on the screen from drying, and is removed when a new original printing stencil is mounted.
As described above, the original printing stencils for respective colors are created by different devices, and after the original printing stencils are manually mounted on the printing drum, a trial printing is conducted to check for printing deviation. Thus, the operation is complex and takes a long time. Further, since it is impossible to adjust the mounting position of the original printing stencil precisely to the preset position, it is difficult to perform a high quality printing operation without causing printing deviation.
In addition, there is the possibility that a new original printing stencil will be stained when the used printing stencil is removed or the new original printing stencil is mounted.